Feed structure for tube mills



Feb. 20, 1951 Filed June 10, 1946 2 Sheets-Sheet 1 Inventor HNOERSO IV H N no PH A Horney aC E I 2,542,875

FEED STRUCTURE FOR TUBE MILLS Feb. 20, 1951 A, MacPHEE 2,542,875

URE-FOR T Filed June 10, 1946 Fl 0. Z.

2 Sheets-Sheet 2 Patented Feb. 20, 1951 FEED STRUCTURE FOR TUBE MILLS Anderson MacPhee, Chesterfield, England, assignor to Mitchell Engineering Limited, London, England, a British company Application June 10, 1946, Serial No. 675,713 In Great Britain July 3, 1945 2Claims. (01.241-1'71) This invention relates to ball tube mills such as are used for grinding coal, limestone and other materials which are to be reduced to a finely powdered form. It is the object of the invention to improve the' construction of such mills, the means of supporting and driving them, and of delivering the materials to be ground thereto.

In a well known type of ball tube mill the material to be ground is introduced through a hollow trunnion, generally with the use of an Archimedeanscrew feed, and there are journal, ball or roller bearings disposed around the hollow trunnion. This arrangement is not altogether satisfactory in use, and one of the features of the present invention is a construction which eliminates the necessity for a hollow trunnion. Other features are concerned with the charging apparatus, a spider through which the material is admitted, and devices for avoiding the accumuiation of material at the entry to the mill.

The invention is illustrated by way of example in the accompanying drawings, in which:

Figure l is a side elevation partly in section of a ball mill constructed according to the invention;

Figure 2 is a detail view of an enlarged scale of a part of the shaft end seen in Figure 1;

Figure 3 is an elevation of the lifters on the drum supporting spider at the feeding end; and Figure 4 is an elevation of the feeding hopper and throat fillers, Figures 3 and 4 looking in opposite directions along the axis of the supporting shaft.

The body of the mill consists of a tube or cylinder l0, generally of steel, which may be of any convenient length, say 9 or feet long, and any suitable diameter such as 4 feet, 6 inches. The mill has a lining of hard steel plates II, which are renewable as they wear, preferably supported on a layer of resilient material l2 which may be cork, India rubber or the like. The middle portion of the cylinder is broken away in the drawings, but will generally embody a removable door or manhole with a bolted flange giving access to the interior for renewing the lining and so forth. The cylinder has flanges cylinder and a spider consisting in this case of four spokes I6 connecting the coned flange to a hub II by which the castings l4 and I5 are respectively mounted on the end of the shaft I8 2 at the driving end, and a stub shaft I9 at the other end. A suitable cross section for the arms [6 is indicated in Figure 1 by showing a portion of the horizontal forwardly projecting arm in section in front of the hub ll.

A suitable feeder delivers the material to be ground to a hopper 2D, whence it falls down a chute 21 with a steeply inclined rear wall leading down to a casting 22 forming a filler between the bottom of the chute and the aperture of the spider in the end casting l4, through which the material to be ground enters the mill. The members 23 are inserted at a substantial angle with respect to the horizontal axis of the shaft and are adapted to deflect material around said shaft and toward the spaces between the arms of the spider. The shaft itself is surrounded by inserted members consisting of castings 23 and 24 above and below which enclose the shaft within the chute and protect it from the falling material. The feed chute 2| and the castings 23 and 24 are divided horizontally at the level of the shaft I8 so that they can be assembled around the shaft and removed at any time for replacement and repair. The filler 22 is inserted in a gland ring 25 which projects into the end of the casting I4, providing a joint between the rotating casting and the stationary feed chute. Suitable packing 26 held in place by a bolted ring 21 provides an effective joint around the gland ring.

In order to prevent material from packing into the lower part of the feed chute where it enters the casting [4 it is preferred to attach to the arms or spokes I6 lifters 28 which extend into the gland ring 25 and keep the material to be ground moving freely therein. For driving purposes the shaft [8 is connected through a coupling 29 and shaft 30 to a gear box 3| containing a reduction gear, the drive for which is provided by a motor on the base. In place of a reduction gear of course any equivalent such as a reduction chain drive can be, used.

The construction at the discharge end may be substantially identical with that at the feed end,

:- the parts in question there shown in Figure 1 being numbered accordingly, but no lifter blades 28 are required, and as the dried material in this case is intended to be extracted by a current of air, the outlet consists of a casing 33 connected to an air trunk 34 which conveys the air and dried ground material to a suitable separator and fan forming no part of this invention. Air suitably heated is introduced with the material to be ground through the hopper 20. In the example of construction shown the shaft I8 is cooled by allowing some cold air to enter through the clearance within the castings 23 and 24, the

vention. They are preferably roller bearings, and-;,

one of the bearings may be mounted so as to float in its supports, thus allowing for expansion and contraction of the drum andspidersdue toheat ing and cooling as is well known theartt, Balls are introduced into the cylinder for grind'ring the material therein, the. approximate level to which the balls are filledbeing indicated by the dotted line at 31 in Figure 1. When in"- 017- eration, the balls are cascading in thecylinder and would be liable to damage the ends of the shafts t8: and I9 if they had direct access therete. In order, to prevent this, protective plates 40, which may be of cast steel say -2. inches-thick, arescrewedon to the projecting ends of theshafts l8 and I9 and locked-by taper dowel pins 41 en} gaging; in the hubs l1, and screwed into. the ends of recessesin the caps (Figure 2). The heads of the dowel pins are thus enclosed in deep recesses, which are then filled by screwed-in plugs 411; so that the dowel pins cannot be damaged until the caps All-are largely worn away, by which time ofi course they will be replaced. Any other convenient means may be adopted for securi ng' the caps Mi, but the construction shown has" been found convenient If'the mill isto be used for grindingmi'nerals without anair current through the mill, s'uitable scoops or;blades (not showril similar to the lifters 2 '8..may' befprovide'dl at the delivery end for discharging material through the spider at this end to a chute (not shown) surrounding the shaft within the gland ring and sloping outwards and downwards, as iswell' known in the art.

When the material" is airborne as described may be; used, whether ofjhard' steeL-m'etalli'c carbifde's; alumina, or ceramic materi'als'i' The type of ball to be used depends of course on the class of material to be ground.

I claim:

1. A grinding mill comprising a cylinder containing a plurality of rolling grinding means, end members supporting said cylinder at each end thereof,- eaclr such endmember comprising a spider with a, Hub portiomandradiating arms surrounded by a coned flange portion expanding toward the interior of said cylinder, shafts supporting the hubportions of said spiders and terminatiiig at the inner faces thereof, means for supportinggsaidshafts outside said cylinder, said means constituting the sole supports for said J cylinders, means: for applying power to one of said shafts afeed chute embracing one of said snart'ssardacnute forming a steeply inclined wall leading toward the spider at the feed end of the cylinder, a stationary inwardly inclined filler beneath said embraced shaft and adapted to deflectincommg material towards cylinder, and a gl'and ringencirclingsaidshait-and: encompassinggsaid filler and providing a joint bee tween said'qchute. and said--conedflange.-

21- A grinding m illaas claimedin claim 1 comeprising also lifters attachedto the-radiatingarms of. said spider and extending; from the outergpe riphery thereof into the path of material de l-ivered by said chute. V I ANDERSON -MAcP-HEE..

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